Aluminum alloy



30 num, magnesium Patented 27, 1930 UNITED STATES PATENT, OFFICE ITBUMZLN S. FULLER AND DAVID BASCH,'OF SGHENECT ADY, NEW YORK, ASSIGNORSTO GENERAL ELECTRIC COMPANY A CORPORATION OF NEW YOBK ALUMINUM ALLOY IoDrawing.

Our present invention comprises an improved castallo of aluminum zincand magnesium, and it is the ob ect of our mvention to improve thephysical properties of the cast alloy.

Heretofore cast aluminum alloys .containa ing copper have been improvedby heat treatment. The improvement has been ascribed to the tendencyof-certain components, par- 1o ticularly copper-aluminum particles, tobe thrown out of solution from the aluminum during the slow coolingafter the heat treatment. I

We have now discovered that aluminum alloy castings containing at leastabout 6% a heat treatment schedule which is hereinafter described indetail. The improvement due to heat treatment is especially marked inthe case of aluminum alloys containing both zinc and magnesium and aneven more marked improvement due to heat treatment is obtained whenother alloying "elements such as iron are present. D

The improvement in mechanical properties due to heat treatment in analloy of alumiand zinc, illustrates the benefits of our invention. Acast alloy comprising about 92.7 5 parts aluminum, about 6 parts zincand about 1.25 parts magnesium, and excluding copper except as anegligible impurity has a tensile strength of about 26,- 000 pounds persquare inch and a hardness of about 75 Brinell. When this alloy isheated to about 515 C. for about twenty-four hours, then is quenched inboiling water, and finally is aged either artificially at about 150 C.for

three hours or more, or naturally the tensile strength is increased toabout 35,000 pounds per square inch and the hardness is raised to about104 Brinell. v

Fuller Patent 1,273,762 of July 23, 1918, covers an aluminum alloycontaining zinc, magnesium and iron, or various described equivalents.In accordance with this patent the cast alloy is mechanically worked, asby iorging, rolling, or drawing. We have dis- Application filed Decemberis, 1923. Serial 110. 680,516. 7 covered that the physical properties ofthe magnesium 1.25%, has without heat treat-' ment a tensile strength ofabout 30,000 pounds and a hardness of 65 Brinell.

In accordancewith our inventionthis cast alloy is given the followingheat treatment:

The alloy first is heated to a temperature of about 450 to 575 C. forabout 24 hours and then is quenched, preferably in boiling water. Nextthe alloy is subjected to an aging treatment, ior example, by heating toa temperature of about 150 C. for about. one to three I hoursor more.Thereafter it may be allowed to cool naturally. As a result "of thisheat treating schedule the properties of the cast alloy are materiallyimproved. The tensile strength-is increased to 50,000 pounds and thehardness is raised to 115 Brinell. In place of iron, or in addition toiron, other alloying metals, including'silicon, may be added to thealloy of aluminum, magnesium and zinc.

In'this specification and in the claims, the terms quenching and a ingare intended to cover not only the speci c temperatures enumeratedherein but also the known variations of these temperatures which arepermissible under various conditions. Forexample, it is known that agingof an alloy can be carried out at a lower temperature if the length ofthe I aging step is correspondingly increased.

What we claim as new and desire to secure by Letters Patent of theUnited States, is,-

1. The method of improving the tensile strength and hardness of analuminum alloy containing atfleast about six per cent zinc,

about one-half to two and one-half per cent 2. A heatrtreated alloy ofaluminum being substantially devoid of cop er and containing about sixper cent zinc, about one and onequarter per cent magnesium and two percent 5 iron said alloy having a tensile strength of about 50,000 poundsper square inch and a hardness of about 155 Brinell but having otherwisesubstantially the properties of cast metal.

o 8. The method of imgroving the tensile strength of a cast alloy w ichis substantially devoid of. copper but contains more than 80% aluminum,at least about 6% zinc and at least about magnesium, which consists 15in heatingltlhe alloy between 450 C. and 57 5 (3., quenc 'ng the alloyand then aging it at a temperature of about 150 C.

In witness whereof, we have hereunto set, our hands this 12th da ofDecember, 1923. so TR S. FULLER.

- 7 DAVID BASOH.

